The present invention relates to high molecular weight linear polyester-based molding compositions.
Molding compositions based on high-molecular weight linear polyesters, in both reinforced and nonreinforced form, are valuable materials for the manufacture of components having very good mechanical properties. A significant disadvantage is their unsatisfactory notch impact strength whereby their range of application is limited in thin-walled molded article uses and/or in molded articles with corners and edges.
To improve notch impact strength, DOS (German Unexamined Laid-Open Application) No. 2,651,560 discloses copolyesters of terephthalic acid, 1,4-butanediol, and a branched, saturated aliphatic dicarboxylic acid of 7-30 carbon atoms. These copolyesters have a greatly reduced melting point compared with poly(butylene terephthalate).
The same disadvantage of a lowered melting point is exhibited by mixtures of poly(butylene terephthalate) and terephthalic acid/sebacic acid/1,4-butanediol copolyesters (DOS No. 2,707,852).
It is further known from DOS No. 2,331,826 to mix aliphatic polylactones with poly(butylene terephthalate). Since the polylactones have a melting range on the order of about 60.degree. C., they produce molding compositions having restricted applications, especially at elevated temperatures or when used over a relatively long period of time.
To improve the impact strength of linear polyesters, DOS No. 2,622,414 describes the addition of up to 20% by weight of an aromatic polycarbonate, wherein one of the components must be present in pulverized form. Similar measures are known from DOS No. 2,348,377. However, according to the latter, it is difficult to disperse such impact-strength-improving components in the polyester in such a way that homogeneous molded articles can be obtained.
Furthermore, poly(alkylene glycols) having an average molecular weight of 600-6000 have been described as a co-component in, for example, poly(butylene terephthalate) (DOS No. 2,725,709). This feature does not result in any change or improvement of the notch impact strength.
By blending linear polyesters with elastomeric segmented copolyesters of terephthalic acid dialkyl ester, alkanediol, and poly(alkylene glycol), the notch impact strength result in any change or improvement of the notch impact strength.
By blending linear polyesters with elastomeric segmented copolyesters of terephthalic acid dialkyl ester, alkanediol, and poly(alkylene glycol), the notch impact strength of molding compositions can be improved. At the same time, other mechanical properties, such as, for example, the rigidity of molded parts manufactured therefrom are considerably impaired (DOS No. 2,363,512).
The use of polyether ester amides for the production of molded articles having a high cold impact strength is known from DOS No. 2,712,987. This reference, however, does not describe the use of such products as a co-component in linear polyesters. Furthermore, this reference does not suggest that molding compositions manufactured from such blends likewise would have an improved notch impact strength.